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<pre><span class="sourceLineNo">001</span><a name="line.1"></a>
<span class="sourceLineNo">002</span>/*<a name="line.2"></a>
<span class="sourceLineNo">003</span> * Copyright (C) 2014 Archie L. Cobbs. All rights reserved.<a name="line.3"></a>
<span class="sourceLineNo">004</span> *<a name="line.4"></a>
<span class="sourceLineNo">005</span> * $Id: BinaryExprParser.html 842 2015-03-07 18:20:42Z archie.cobbs $<a name="line.5"></a>
<span class="sourceLineNo">006</span> */<a name="line.6"></a>
<span class="sourceLineNo">007</span><a name="line.7"></a>
<span class="sourceLineNo">008</span>package org.jsimpledb.parse.expr;<a name="line.8"></a>
<span class="sourceLineNo">009</span><a name="line.9"></a>
<span class="sourceLineNo">010</span>import java.util.ArrayList;<a name="line.10"></a>
<span class="sourceLineNo">011</span>import java.util.Arrays;<a name="line.11"></a>
<span class="sourceLineNo">012</span>import java.util.List;<a name="line.12"></a>
<span class="sourceLineNo">013</span><a name="line.13"></a>
<span class="sourceLineNo">014</span>import org.jsimpledb.parse.ParseContext;<a name="line.14"></a>
<span class="sourceLineNo">015</span>import org.jsimpledb.parse.ParseException;<a name="line.15"></a>
<span class="sourceLineNo">016</span>import org.jsimpledb.parse.ParseSession;<a name="line.16"></a>
<span class="sourceLineNo">017</span>import org.jsimpledb.parse.Parser;<a name="line.17"></a>
<span class="sourceLineNo">018</span>import org.jsimpledb.parse.SpaceParser;<a name="line.18"></a>
<span class="sourceLineNo">019</span><a name="line.19"></a>
<span class="sourceLineNo">020</span>/**<a name="line.20"></a>
<span class="sourceLineNo">021</span> * Support superclass for tail-recursive binary expression parsers for expressions of the form {@code ARG1 OP ARG2}.<a name="line.21"></a>
<span class="sourceLineNo">022</span> *<a name="line.22"></a>
<span class="sourceLineNo">023</span> * @see &lt;a href="http://en.wikipedia.org/wiki/Tail_recursive_parser"&gt;Tail Recursive Parser&lt;/a&gt;<a name="line.23"></a>
<span class="sourceLineNo">024</span> */<a name="line.24"></a>
<span class="sourceLineNo">025</span>public abstract class BinaryExprParser implements Parser&lt;Node&gt; {<a name="line.25"></a>
<span class="sourceLineNo">026</span><a name="line.26"></a>
<span class="sourceLineNo">027</span>    private final SpaceParser spaceParser = new SpaceParser();<a name="line.27"></a>
<span class="sourceLineNo">028</span>    private final Parser&lt;? extends Node&gt; lowerLevel;<a name="line.28"></a>
<span class="sourceLineNo">029</span>    private final boolean leftAssociative;<a name="line.29"></a>
<span class="sourceLineNo">030</span>    private final List&lt;Op&gt; ops;<a name="line.30"></a>
<span class="sourceLineNo">031</span><a name="line.31"></a>
<span class="sourceLineNo">032</span>    /**<a name="line.32"></a>
<span class="sourceLineNo">033</span>     * Primary constructor.<a name="line.33"></a>
<span class="sourceLineNo">034</span>     *<a name="line.34"></a>
<span class="sourceLineNo">035</span>     * @param lowerLevel next lower parse level<a name="line.35"></a>
<span class="sourceLineNo">036</span>     * @param leftAssociative true for left-to-right association, false for right-to-left<a name="line.36"></a>
<span class="sourceLineNo">037</span>     * @param ops operations, with operations that have other operations as prefixes listed first<a name="line.37"></a>
<span class="sourceLineNo">038</span>     */<a name="line.38"></a>
<span class="sourceLineNo">039</span>    protected BinaryExprParser(Parser&lt;? extends Node&gt; lowerLevel, boolean leftAssociative, Op... ops) {<a name="line.39"></a>
<span class="sourceLineNo">040</span>        if (lowerLevel == null)<a name="line.40"></a>
<span class="sourceLineNo">041</span>            throw new IllegalArgumentException("null lowerLevel");<a name="line.41"></a>
<span class="sourceLineNo">042</span>        if (ops == null || ops.length == 0)<a name="line.42"></a>
<span class="sourceLineNo">043</span>            throw new IllegalArgumentException("null/empty ops");<a name="line.43"></a>
<span class="sourceLineNo">044</span>        this.lowerLevel = lowerLevel;<a name="line.44"></a>
<span class="sourceLineNo">045</span>        this.leftAssociative = leftAssociative;<a name="line.45"></a>
<span class="sourceLineNo">046</span>        this.ops = Arrays.asList(ops);<a name="line.46"></a>
<span class="sourceLineNo">047</span>    }<a name="line.47"></a>
<span class="sourceLineNo">048</span><a name="line.48"></a>
<span class="sourceLineNo">049</span>    /**<a name="line.49"></a>
<span class="sourceLineNo">050</span>     * Convenience constructor for left-associative operators.<a name="line.50"></a>
<span class="sourceLineNo">051</span>     *<a name="line.51"></a>
<span class="sourceLineNo">052</span>     * @param lowerLevel next lower parse level<a name="line.52"></a>
<span class="sourceLineNo">053</span>     * @param ops operations, with operations that have other operations as prefixes listed first<a name="line.53"></a>
<span class="sourceLineNo">054</span>     */<a name="line.54"></a>
<span class="sourceLineNo">055</span>    protected BinaryExprParser(Parser&lt;? extends Node&gt; lowerLevel, Op... ops) {<a name="line.55"></a>
<span class="sourceLineNo">056</span>        this(lowerLevel, true, ops);<a name="line.56"></a>
<span class="sourceLineNo">057</span>    }<a name="line.57"></a>
<span class="sourceLineNo">058</span><a name="line.58"></a>
<span class="sourceLineNo">059</span>    @Override<a name="line.59"></a>
<span class="sourceLineNo">060</span>    public Node parse(ParseSession session, ParseContext ctx, boolean complete) {<a name="line.60"></a>
<span class="sourceLineNo">061</span><a name="line.61"></a>
<span class="sourceLineNo">062</span>        // Gather sub-nodes and intervening operators<a name="line.62"></a>
<span class="sourceLineNo">063</span>        final ArrayList&lt;Node&gt; nodeList = new ArrayList&lt;&gt;(2);<a name="line.63"></a>
<span class="sourceLineNo">064</span>        final ArrayList&lt;Op&gt; opList = new ArrayList&lt;&gt;(1);<a name="line.64"></a>
<span class="sourceLineNo">065</span>        nodeList.add(this.lowerLevel.parse(session, ctx, complete));<a name="line.65"></a>
<span class="sourceLineNo">066</span>        while (true) {<a name="line.66"></a>
<span class="sourceLineNo">067</span>            this.spaceParser.parse(ctx, complete);<a name="line.67"></a>
<span class="sourceLineNo">068</span>            final int mark = ctx.getIndex();<a name="line.68"></a>
<span class="sourceLineNo">069</span>            Op op = null;<a name="line.69"></a>
<span class="sourceLineNo">070</span>        candidateLoop:<a name="line.70"></a>
<span class="sourceLineNo">071</span>            for (Op candidate : this.ops) {<a name="line.71"></a>
<span class="sourceLineNo">072</span>                if (ctx.tryLiteral(candidate.getSymbol())) {<a name="line.72"></a>
<span class="sourceLineNo">073</span>                    op = candidate;<a name="line.73"></a>
<span class="sourceLineNo">074</span>                    break;<a name="line.74"></a>
<span class="sourceLineNo">075</span>                }<a name="line.75"></a>
<span class="sourceLineNo">076</span>            }<a name="line.76"></a>
<span class="sourceLineNo">077</span>            if (op == null)<a name="line.77"></a>
<span class="sourceLineNo">078</span>                break;<a name="line.78"></a>
<span class="sourceLineNo">079</span>            this.spaceParser.parse(ctx, complete);<a name="line.79"></a>
<span class="sourceLineNo">080</span>            final Node rhs;<a name="line.80"></a>
<span class="sourceLineNo">081</span>            try {<a name="line.81"></a>
<span class="sourceLineNo">082</span>                rhs = this.lowerLevel.parse(session, ctx, complete);<a name="line.82"></a>
<span class="sourceLineNo">083</span>            } catch (ParseException e) {<a name="line.83"></a>
<span class="sourceLineNo">084</span>                if (complete &amp;&amp; !e.getCompletions().isEmpty())<a name="line.84"></a>
<span class="sourceLineNo">085</span>                    throw e;<a name="line.85"></a>
<span class="sourceLineNo">086</span>                ctx.setIndex(mark);                             // backtrack<a name="line.86"></a>
<span class="sourceLineNo">087</span>                break;<a name="line.87"></a>
<span class="sourceLineNo">088</span>            }<a name="line.88"></a>
<span class="sourceLineNo">089</span>            nodeList.add(rhs);<a name="line.89"></a>
<span class="sourceLineNo">090</span>            opList.add(op);<a name="line.90"></a>
<span class="sourceLineNo">091</span>        }<a name="line.91"></a>
<span class="sourceLineNo">092</span>        if (nodeList.size() == 1)<a name="line.92"></a>
<span class="sourceLineNo">093</span>            return nodeList.get(0);<a name="line.93"></a>
<span class="sourceLineNo">094</span><a name="line.94"></a>
<span class="sourceLineNo">095</span>        // Build AST<a name="line.95"></a>
<span class="sourceLineNo">096</span>        Node node;<a name="line.96"></a>
<span class="sourceLineNo">097</span>        if (this.leftAssociative) {<a name="line.97"></a>
<span class="sourceLineNo">098</span>            node = this.createNode(opList.get(0), nodeList.get(0), nodeList.get(1));<a name="line.98"></a>
<span class="sourceLineNo">099</span>            for (int i = 1; i &lt; nodeList.size() - 1; i++)<a name="line.99"></a>
<span class="sourceLineNo">100</span>                node = this.createNode(opList.get(i), node, nodeList.get(i + 1));<a name="line.100"></a>
<span class="sourceLineNo">101</span>        } else {<a name="line.101"></a>
<span class="sourceLineNo">102</span>            final int max = nodeList.size();<a name="line.102"></a>
<span class="sourceLineNo">103</span>            node = this.createNode(opList.get(max - 2), nodeList.get(max - 2), nodeList.get(max - 1));<a name="line.103"></a>
<span class="sourceLineNo">104</span>            for (int i = max - 3; i &gt;= 0; i--)<a name="line.104"></a>
<span class="sourceLineNo">105</span>                node = this.createNode(opList.get(i), nodeList.get(i + 1), node);<a name="line.105"></a>
<span class="sourceLineNo">106</span>        }<a name="line.106"></a>
<span class="sourceLineNo">107</span><a name="line.107"></a>
<span class="sourceLineNo">108</span>        // Done<a name="line.108"></a>
<span class="sourceLineNo">109</span>        return node;<a name="line.109"></a>
<span class="sourceLineNo">110</span>    }<a name="line.110"></a>
<span class="sourceLineNo">111</span><a name="line.111"></a>
<span class="sourceLineNo">112</span>    protected Node createNode(final Op op, final Node lhs, final Node rhs) {<a name="line.112"></a>
<span class="sourceLineNo">113</span>        return new Node() {<a name="line.113"></a>
<span class="sourceLineNo">114</span>            @Override<a name="line.114"></a>
<span class="sourceLineNo">115</span>            public Value evaluate(ParseSession session) {<a name="line.115"></a>
<span class="sourceLineNo">116</span>                return op.apply(session, lhs.evaluate(session), rhs.evaluate(session));<a name="line.116"></a>
<span class="sourceLineNo">117</span>            }<a name="line.117"></a>
<span class="sourceLineNo">118</span>        };<a name="line.118"></a>
<span class="sourceLineNo">119</span>    }<a name="line.119"></a>
<span class="sourceLineNo">120</span>}<a name="line.120"></a>
<span class="sourceLineNo">121</span><a name="line.121"></a>




























































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